Researchers at the Smithsonian Conservation Biology Institute have discovered why older females are rarely able to reproduceand hope to use this information to introduce vital new genes into the pool. SCBI scientists and collaborating researchers analyzed hormones, eggs and the uteri of 34 cheetahs at eight institutions, and determined that while the hormones and eggs of cheetahs older than 8 years appear normal, the animals' uterine tracks tend to suffer from abnormal cell growth, infections and cysts that prevent pregnancy.
"Those of us who work with cheetahs have anecdotally noted that it's hard to reproduce older cheetahs, but this is the first time anyone has documented how aging affects the physiology of reproduction in this species," said Adrienne Crosier, SCBI cheetah biologist and lead author of the study in which these results were published. "We were relieved to find that, unlike in other older mammals, the eggs in older cheetahs can produce viable-appearing and growing embryos, which means we may be able to transfer them to younger cheetahs and preserve genetic diversity. If we had found that the eggs were abnormal, we were facing losing genes in an already depleted population."
The researchers' findings were published in a paper titled Increasing Age Influences Uterine Integrity, But Not Ovarian Function or Oocyte Quality, in the Cheetah (Acinonyx jubatus) in the online version of the Biology of Reproduction in May and in final form this month. According to the study, approximately 80 percent of adult female cheetahs in North American institutions have never reproduced and the death rate for cheetahs has exceeded the birth rate in 13 of the last 16 years. Lack of genetics can lead to cub mortality and lower cheetahs' resistance to disease.
The next step for SCBI researchers is to extract eggs from a cheetah older than 8 years that has not reproduced and to fertilize the eggs and transfer them to a younger female.
|Contact: Lindsay Renick Mayer|